Bjork's Journey with her Sketchbook :)

[Mechanizoid]

I know it's always tough to struggle with things you aren't good at–but going outside your comfort zone is what makes you grow! :) I don't have much advice on rendering cliffs. But all you need to do is keep doing what you are doing. And again, that last BW cliff you did from memory is much better than the study. That's funny, usually it is the other way around!